The fast-growing legal sports betting industry is extending its reach to the middle of the ocean.

BetMGM and Online Casino Carnival Corporation announced a deal Friday to put sports books on more than 50 U.S.-based ships.

The arrangement will allow betting while the ships are at sea or while docked at a port in a state that allows sports betting. Passengers can bet using a mobile app or at physical kiosks on the ship.

It encompasses the Carnival Cruise Line, Online Casino Holland America Line and Princess Cruises.

Princess began offering sports betting last October.

The sports betting operations will be phased in over the next few months, BetMGM said.

"We_ve found an ideal partner in Carnival Corporation and look forward to providing our sports betting and iGaming products to its millions of passengers," BetMGM CEO Adam Greenblatt said in a statement.